This invention relates to packet communications systems and, more particularly, to methods and apparatus for the central management of routing paths in such systems.
The supervision of packet transmission networks is typically assigned to one individual with special skills in network management. Such network supervisors typically are located at one node of the network and have the responsibility of insuring the proper operation of the network to insure network services to all users of the network. Many supervisory functions, however, must take place at other nodes of the network. The establishment of connections, and the testing of those connections, for example, must be initiated by one of the nodes in the route of the connection, typically the source node. In order to centrally manage the establishment, discontinuation and restoral of routes or paths through the network for the transmission of data between users of the network, is therefore necessary to provide a mechanism for remotely monitoring, establishing, terminating and reassigning such routes from a centrally located supervisory or manager node in the network. The central node is typically called the Manager node and all other nodes are called Agent nodes. Routes between Agent nodes are created at the originating Agent node of the route and such nodes are specified either by the name of the destination node (called a named route), or by the specification of the sequence of nodes and transmission links making up the route (called a connection route). In either case, it is desirable to set up routes remotely from a centralized manager node to accommodate link failures, congestion or the need to take resources out of service.
The most common control command mechanism available for managing packet networks from a central location utilizes xe2x80x9cSETxe2x80x9d (set a value from a remote location) and xe2x80x9cGETxe2x80x9d or xe2x80x9cGET_NEXTxe2x80x9d (retrieve a value from a remote location) commands. One such command structure is known as the Simple Network Management Protocol (SNMP). In the SNMP system, a simple xe2x80x9cGETxe2x80x9d or xe2x80x9cGET_NEXTxe2x80x9d command is used to obtain a single value from a remote node in the packet network. Similarly, a simple xe2x80x9cSETxe2x80x9d command is used to set a single value in a remote node of the packet network. Unfortunately, this simple command structure does not lend itself well to creation, deletion and alteration of routes as is necessary for overall route management. In the prior art systems utilizing such a limited command structure, it is difficult or impossible to centrally manage route changes in the entire packet transmission system. Without central management, each node must manage all of the routes originating at that node, requiring duplication of the management facilities at each of the nodes, thereby increasing the cost and complexity and reducing the throughput of the network.
Attempts to centrally manage routing paths using these standard manager-agent interaction commands suffers from a number of problems. The network manager, for example, has no way of knowing which routes have been changed dynamically due to a transmission or device failure, or how often such changes have occurred. Similarly, the network administrator has no way to initiate the re-calculation of a route after a failed resource has been restored to service, or to specify that a certain route be used.
In accordance with the illustrative embodiment of the present invention, a path management system is provided which provides central management of connection routing in systems having a limited protocol control command structure. More particularly, a data object called a path object is defined as a read-write data value and is specified for each path originating at a particular node. A table of such path objects, called the path table, is established in each Agent node of the network. These data objects, which can be set to any desired value remotely by use of a xe2x80x9cSETxe2x80x9d command, are used to initiate the creation or deletion of data routes. That is, each path data object is monitored by the local Agent node and, when a change in value is detected, a new path is generated, identified by the new value in the path data object. Each path data object in the path table includes fields identifying the identification of the path, the route of the path, and administrative information such as, for example, the number of packets traveling in each direction on that path.
In further accord with the present invention, a path status data table is maintained at all of the Agent nodes which are end-points of path routes. A new status entry in the path status table is created each time a route is deleted or modified. Each status entry in the path status table contains a plurality of fields specifying the identification of the path, the time of establishment, the route of the old path, the route of the new path, the reason for the new path being created, and the result of the attempt to create the path, i.e., success or failure. A new entry is created in the path status table, not only when the centralized path Manager node directs the creation of a new path, but also when the new path is created in response to the Agent node""s own path creation algorithms.
The Manager node, Agent node interactions are entirely independent of the supervisory control command structure used. As suggested above, the SMNP management protocol can be used. Other management command structures can also be used, including the Common Management Information Protocol (CMIP), the System Network Administration, Management Services (SNA/MS) protocol, and many other proprietary command protocols.
A further advantage of the present invention is the independence of the route management system from the actual routing protocols used by the Agent nodes. Indeed, different nodes could use different routing algorithms and still participate in the centralized routing management system of the present invention. For example, the High Performance Routing (HPR) protocol can be used, as well as other Link State routing protocols such as the Advanced Peer-to-Peer Networking (APPN) protocol, the Open Shortest Path First (OSPF) protocol, used by the Transmission Control Program, Internet Protocol (TCP/IP), and the Intermediate System to Intermediate System (IS-IS) protocol, used by Open Systems Interconnect (OSI) and TCP/IP.
It can be seen that the path management techniques of the present invention make it possible to centrally manage all of the routes in an entire packet network from a single route management node, using only a simple SNMP-like command structure. This centralized route management reduces duplication, cost, and complexity of the route management function.